BPK 110 Human Nutrition: Current Issues Lecture 5b - TOPICS

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1 BPK 110 Human Nutrition: Current Issues Lecture 5b - TOPICS 1. Functions of Protein in the Body 2. Protein: Quality, Use and Needs 3. Protein Deficiency/Excess 4. Adult Protein Energy Malnutrition (PEM) 5. Protein & Amino Supplementation? 1

2 Learning Objectives To describe and explain the various functions of proteins and amino acids in the body To describe how enzymes catalyze biochemical reactions in the body To describe digestibility of protein and measures of protein quality To clearly describe types and consequences of protein malnutrition in children and adults Copyright 2018 by Nelson Education Ltd. 2

3 1. Functions of Protein in the Body multiple function of protein in human body including: (a) Growth & Maintenance: for new tissues including blood, skin, muscle, (b) Immune System Antibodies: self vs nonself; antigen memory (c) Maintenance of Acid/Base + Fluid & Electrolyte balances: - act as buffers - buffers mop up extra hydrogen atoms (H + ) when ph is too low (i.e. high acidity), donate H + when ph is too high (low acidity) -recall acidosis is alkalosis is -proteins influence fluid movement in/out body s compartments 3

4 1. Functions of Protein in the Body Continued (d) Enzymes: to catalyze chemical reactions. Figure 6-9 Enzyme Action 4

5 1. Functions of Protein in the Body Continued (e) Hormones: e.g. Insulin & Glucagon are protein hormones 5

6 1. Functions of Protein in the Body Continued (f) Maintenance of Fluid & Electrolyte Balance -protein charged surface holds water in cells -prevents edema 2003 Wadsworth, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license. 6

7 (h) Energy Source: in conditions of CHO/Lipid deficiency Amine groups converted to urea in liver and excreted by the kidneys Carbon fragments 7 used as energy source

8 2. Protein: Quality, Use and Needs (a) Digestibility of Protein Animal proteins > 90% Legumes >80% Grains/Plant Foods = 60-90% (see next slide for cooking method & digestibility of protein) (b) Protein Quality: depends on amino acid content, protein synthesis & amino acid pool. missing an essential aa? limits protein synthesis this is a.. limiting amino acid Analogy: spelling words with missing vowels e.g. B_K 110 F_RS_ C_L_BR_T N _F L RN_ N G _S _ N O_T _0th 8

9 2. Protein: Quality, Use and Needs Cont 2003 Wadsworth, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license. Cooking with moist heat improves protein digestibility, whereas frying (dry heat) makes protein harder to digest. 9

10 2. Protein: Quality, Use and Needs Cont Partially completed proteins are dismantled important to get all essential aa s in the diet (c) Mutual Supplementation & Complementary Proteins Mutual Supplementation -eat variety of protein sources to get a full complement of aas. e.g. 2 proteins each with missing essential aa s but together they give all essential aa s In this strategy 2 incomplete proteins are called complementary proteins i.e. together 2 or more proteins sources provide all the essential aa s (Fig 6-3). complementary proteins can be eaten within the same day. 10

11 11

12 2. Protein: Quality, Use and Needs Cont (d) Measuring Protein Quality (i) Protein Digestibility-Corrected Amino Acid Score (PDCAAS) -protein content is not sufficient -digestibility of protein + proportion of aa s need to be considered PDCAAS is scale of 100 to = most digestible protein w/ perfectly balanced aa s for human. e.g s egg white, ground beef, chicken products, tuna fish - Soybean: 94, Legumes: ~50-60, Gluten (wheat protein) 25 - Combine pea flour (PDCAAS = 67) + whole wheat flour (PDCAAS = 40), gives PDCAAS=82 (Mutual Supplementation) (ii) Protein Efficiency Ratio (PER)-measures quality in infant foods 12

2. Protein: Quality, Use and Needs Cont (e) Protein RDA

8 g/kg body weight -depends on body size; levels for

zero balance of (nitrogen in - nitrogen out = 0) (+)

13 2. Protein: Quality, Use and Needs Cont (e) Protein RDA (Table 6-1) RDA = 0.8 g/kg body weight -depends on body size; levels for pregnant women & children Based on nitrogen balance studies: -nitrogen in (N in food) vs. nitrogen out (N sweat, feces/urine, skin) -looking for zero balance of (nitrogen in - nitrogen out = 0) (+) balance = nitrogen in > nitrogen out = gaining protein (-) balance = nitrogen in < nitrogen out = losing protein 13 Figure 6-15 Nitrogen Balance

14 (e) Adult Protein Intake (Table 6-1 Part A) 14

15 (e) Adult Protein Intake (Table 6-1 Part B) 15

o. 1st child, after 2 nd child is born $ breast milk protein; edema/skin

16 3a) Protein Deficiency/Excess Protein Energy Malnutrition (PEM): 2 classes in children immune fxns impaired: $antibody production Kwashiorkor: 1-3 y.o. 1st child, after 2 nd child is born $ breast milk protein; edema/skin rash Marasmus: < 2 y.o. shriveled & lean $ calories & protein/starvation 16

The edema & enlarged liver characteristic of kwashiorkor are evidenced

17 2003 Wadsworth, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license. The edema & enlarged liver characteristic of kwashiorkor are evidenced bythese children s swollen bellies. Malnourished children often have an enlarged abdomen from parasites as well 17

18 2003 Wadsworth, a division of Thomson Learning, Inc. Thomson Learning is a trademark used herein under license. The extreme loss of muscle and fat characteristic of marasmus is apparent in this child s matchstick arms. 18

19 Table 6-3 Features of Marasmus and Kwashiorkor in Children 19

20 Adult Protein Energy Malnutrition (PEM) & Body Defenses 20

21 4) Malnutrition & Immunity (S,W&P Tab 11-1) Adult Protein Energy Malnutrition (PEM) & Body Defenses System Skin GI & body linings Lymph tissues General Response Effect of PEM thin with $ connective tiss. = $ barrier + slow sensitivity to antigens $ antibody secretions & $ immune cell # $ thymus, lymph nodes, spleen size; depleted immune cell # prolonged invader (i.e. antigens) kill time $ circulating immune cell # 21

22 5. Protein & Amino Acid Supplementation? -benefits supplements of single aa s?? -digestion & absorb whole proteins vs. single aa s -excess aa s ties up carriers in blood -better is slow absorption of differing di- & tri-peptides -fatalities on aa supplements e.g tryptophan (see Consumer Corner p. 222 S,W&P ver 3) DRI values for aa & protein supplements is ongoing Little research available on this topic -currently no level of aa supplementation can be assumed to be safe 22

23 Summary Lecture 5b 1. Functions of Protein in the Body 2. Protein: Quality, Use and Needs 3. Protein Deficiency/Excess 4. Adult Protein Energy Malnutrition (PEM) 5. Protein & Amino Supplementation? 23

What Are Proteins? Lecture 9: Proteins. Proteins: large complex molecules composed of amino acids. Nutrition 150 Shallin Busch, Ph.D.

What Are Proteins? Lecture 9: Proteins Nutrition 150 Shallin Busch, Ph.D. Proteins: large complex molecules composed of amino acids. Contain carbon, hydrogen, oxygen, nitrogen Primary source of nitrogen